The present invention relates to an apparatus for sorting and processing tobacco leaves and in particular to an apparatus for sorting and grading tobacco leaves providing improved means for optically sensing leaf of a selected color.
In the tobacco industry, it is necessary to grade tobacco leaves according to various standards such as color, size, type, etc. Such grading has, until recently, been done entirely by hand by individuals who stand before moving conveyor belts in which the leaves are carried from a central loading point and who are required to manually remove from off the conveyor the unwanted leaves, i.e., those leaves of the wrong color, texture and/or degree of uniformity. Due to the large quantity of leaves that must be graded in a given season, the short period of time during which the individual can observe the leaves as they pass by him on the conveyor, the lack of trained grading personnel, etc., there results that many unwanted leaves pass by unobserved.
Recently a number of automatic methods have been proposed for sorting and processing tobacco leaves. In U.S. Pat. No. 3,368,568, there is disclosed a grading apparatus for tobacco leaf which makes use of the differential centrifugal force developed in a leaf as between its heavier stem and lighter tissue to orient the leaf in a predetermined direction and then uses centrifugal force on the oriented leaf to maintain the leaf in a precisely located vertical plane as it passes by a grading station where photo-electric sensing means differentiates the passing leaves according to the presence or absence of a given quality. An air ejection system is provided to remove any sensed improper leaf. This system, however, suffers from the disadvantage that a large turntable is required in order to provide sufficient room for adequate separation.
According to a later patent, U.S. Pat. No. 3,380,460, a grading apparatus for tobacco leaf is provided, which effects an automatic ejection of unwanted leaves by the use of photo-electric sensing means dictating to a leaf ejecting apparatus through an electronic signal differentiating device, in which a linear table is employed dropping leaf through a number of gates. The latter system has the disadvantage of a complicated and complex table and gate arrangement.
More recently, an apparatus has been proposed wherein the electronic and photo-detection system enables the feeding of tobacco to a flat linearly moving belt. However, here too, the tobacco pieces must be separated by a given distance from its preceding and succeeding piece.
At the front end of the belt the tobacco passes over an end plate and is scanned by one or more detectors located in a housing mounted above the table. The detectors are equipped with a testing member for the color of the individual leaves and with a signalling member controlled by the testing member for indicating the color class for the actuation of the classifying device for the leaves.
The disadvantages of this apparatus are associated with the nature, arrangement and positioning of the end plate with respect to the conveyor, the plate being curved somewhat and spaced from the conveyor resulting in the accumulation of leaves in the space with resultant jamming of the apparatus, in turn necessitating interruptions for cleaning out the space before further processing can be carried out. Further, optical testing devices selectively responding to the color of leaves have the disadvantage that they must continuously be adjusted with respect to the color on the basis of which the classification is being carried out. This also involves interruptions in operation to permit the necessary adjustments and in many instances also prolongs the classification process.
In our copending application (see below) to which reference can be made, entitled "Method and System for Grading Articles to Color," filed on even date herewith, an improved photo-detection system and apparatus are disclosed in which the light transmissivity or remission of the tobacco leaf is sensed rather than its intrinsic color. This system is far simpler, more efficient and inherently faster than any known system.
It is the object of the present invention to provide certain structural devices for use with the system described in the foregoing application. In particular it is the object of the present invention to provide an improved end plate, an improved transmissivity or remission guide and criteria, an improved light source for illuminating the end plate, an improved housing for the detection system and an improved detection system as well.
It is another object of the present invention to overcome the defects of the prior art and to provide an improved tobacco leaf grading table for use with the device of the aforementioned application.
These and other objects of this invention will become apparent from the following detailed description.